1. Technical Field
The invention relates generally to cold cathode luminescent field emission devices and, particularly, to a field emission double-plane light source employing a getter to exhaust unwanted gas from therein, thereby ensuring a high degree of vacuum. The invention also relates to a method for making a field emission double-plane light source.
2. Discussion of Related Art
Recently, with the development of various plane display technologies, field emission display (FED) technology has been paid more attention, as well. FED technology potentially offers, e.g., higher brightness, lower energy consumption, broader visual angle, and higher contrast than possible with liquid crystal or plasma displays. FED technology could be utilized in many fields including, e.g., personal computers, mobile communications, flat screen display/televisions, etc. In the plane display technology, a single plane display is typically used to display in a determined direction. However, for, e.g., traffic lights, information displays used in public, a display operating in two opposite directions is required. For solving this problem, two single plane displays are arranged in two opposite directions to display in the two directions. However, this arrangement typically increases the cost and decreases the reliability of the plane display.
In order to decrease the cost of the plane display displaying in two opposite directions and improving the performance of the plane display, a field emission double-plane light source can be employed in a field emission display as a light source. A nanotube-based field emission double-plane light source usually includes a pair of anodes and a cathode arranged between the anodes. The cathode has a pair of electron emission layers on two opposite surfaces thereof, and each of the electron emission layers has a plurality of the carbon nanotubes associated therewith. The anodes each have a respective fluorescent layer facing the corresponding electron emission layers of the cathode. In use, a strong electrical field is provided between the cathode and the anodes, the field excites the carbon nanotubes of the cathode to emit electrons, and the electrons bombard the fluorescent layers of the anodes to thereby produce visible light in two opposite directions.
For a field emission double-plane light source, a high degree of vacuum within an inner portion (i.e., interior) thereof is a virtual necessity. In general, the better of the degree of vacuum of the field emission double-plane light source that is able to be generated and maintained within the field emission double-plane light source during the sealing process and/or thereafter during use, the better the field emission performance thereof is. To maintain the degree of vacuum of the field emission double-plane light source within a desired range, a conventional way is to provide a getter in the inner portion thereof. Such a getter is able to exhaust a gas produced by the fluorescent layer and/or any residual gas remaining within the field emission double-plane light source upon sealing and evacuation thereof. The getter is generally selected from a group consisting of non-evaporable getters and evaporable getters.
For the evaporable getter, a high temperature evaporating process has to be provided during the fabrication of the field emission double-plane light source, and a plane arranged in the inner portion of the field emission plane source has to be provided to receive the evaporated getter. Thus, the cost of the fabrication of the field emission double-plane light source increases, and the cathode and the anodes are prone to shorting during the high temperature evaporating process, thereby causing the failure of the field emission double-plane light source. For the non-evaporable getter, it is typically focused/provided on sidewalls of the field emission double-plane light source, and, thus, the degree of vacuum of portions away from the getter tends to be poorer, in the short-term, than that of portions near to the getter, at least until internal equilibrium can reached, thereby decreasing the field emission performance of the field emission double-plane light source or at least potentially resulting in a fluctuating performance thereof.
What is needed, therefore, is a field emission double-plane light source that overcomes the above-mentioned shortcomings to ensure a high degree of vacuum thereof, thus providing a better and more steady field emission performance during the use thereof.
What is also needed is a method for making such a field emission double-plane light source.